The present invention relates generally to synchronization of clocks and, more particularly, to synchronization of clocks within a network node or element, for example within a chassis including multiple line cards.
It may be advantageous for devices in a networked system to have a common time base. The common time base may be used, for example, to trigger coordinated measurement instances in a network of sensors or to coordinate actions of controllers in an industrial system. In addition to sensors and controllers, the system may include computers and communication devices, such as routers. The electronics industry has developed several standard protocols for use in synchronizing clocks, for example, the Precision Time Protocol (PTP) of IEEE 1588. PTP includes sending timing-related messages between nodes in a communication network.
Errors and inaccuracies may result from unaccounted for delays in distributing a local clock signal within a node, however. That is, a local clock or a pulse synchronizing local clocks distributed from a central module to modules within the node may encounter different delays in transmission to different modules within the node, which may result in different modules of a node having a module dependent timestamp offset that is difficult to compensate for. Accounting for module dependent variations may be difficult, particularly if delays may vary over time or if modules include varying numbers of internal buffers buffering the local clock or synchronizing pulse.